This invention relates generally to an improved building of precast concrete panel construction, and more particularly to such a building with inherent resistance to cracking, spalling, and other deteriorative reaction to the influence of temperature extremes, weather conditions, siesmic forces, and the like.
Precast concrete panels, reinforced with steel, have been used for some time in building construction to take advantage of the desirable properties of concrete as a building material. In presently employed building techniques, however, rigid structural ties are used between precast wall panels, as well as between the panels and building roofs and foundations, and this practice results in cracking, spalling, and/or other deterioration of the concrete after it has been subjected to ambient temperature variations and the influence of strong winds, siesmic movements, etc., over a period of time, sometimes of relatively short duration. One reason for this is the tendency of concrete to expand in all directions under heat excitation and the consequent creation of structural stresses in rigid connections between the panels or between the panels and other parts of the building. Because the connections are rigid, something must eventually give, either the connections themselves or the panels at their weakest points (or at predictable intervals). Damage to the panels also occurs when they are subjected to erratic wind, siesmic, or other forces which cause strains at rigid points of connection therebetween leading to breakage of the panel connections and/or cracking, spalling, etc., of the panels themselves.
The exterior walls of buildings of precast concrete panel construction are often provided with a decorative skin of stucco or the like. This skin is normally applied to the building walls after they are erected, a rather expensive process, involving relatively high labor costs. The stucco, or equivalent, skin is adherent to the concrete walls surfaces, and thus all stresses and strains on the walls as a result of temperature, weather, siesmic, etc., influences is transmitted directly thereto. Consequently, any cracking, spalling, or other unsightly damage to the walls as a result of such stresses and strains is likewise transmitted directly to the skin. Finally, the stucco-coated walls of conventional concrete panel buildings have little insulative protection from ambient temperature changes since the stucco skins, or coatings, of these walls have essentially no insulating ability. Thus, such walls are exposed to approximately the full range of temperature variation between furnace-like summer days and freezing winter nights, and are thereby subject to a high probability of damage as a result of the interaction of rigidly fastened concrete panels under such conditions.
To summarize, concrete has many advantages as a building material, but it also has characteristics which lead to its gradual deterioriation when employed in presently conventional precast concrete panel buildings. An economical means of utilizing precast concrete panels for the construction of buildings in a way to negate these disadvantages, and thus realize the full potential of concrete as a strong, free-form building material, would be a boon to the building industry. If such means could be provided which would permit a reduction in building costs below the costs of conventional precast concrete panel construction work, everyone involved, including, in particular, home buyers, would benefit. To date, however, no way of accomplishing these highly desirable results has, to my knowledge, been proposed.